The present invention relates to a phosphate adsorbent comprising an MgO-TiO.sub.2 complex.
Patients suffering from functional disturbance in kidney or liver are increasing recently. These patients have a weak function to excrete waste metabolites out of a body system, so that such waste materials are accumulated in the system to cause various physiological troubles. Therefore, means and treatments for improving conditions of the patients suffering from such functional disturbance have been performed by removing such waste metabolites.
Chronic renal failure is a typical cases of functional disturbance of kidney. At present, methods such as hemocatharsis by a dialysis membrane and hemoperfusion by active carbons are applied for treatments of the renal failure.
The patients with chronic renal failure have weak renal function to excrete phosphate into urine. However, said hemocatharsis using a dialysis membrane is incapable of sufficiently controlling the phosphate concentration in blood and quite ineffective for the adsorption of phosphate in an intestinal tract. On the other hand, the adsorption method using active carbons has the problem that adsorptivity of inorganic substance such as phosphate is very poor comparing with adsorptivity of organic substance, due to the nature of active carbons.
Accordingly, the patients with chronic renal failure cannot avoid suffering from hyperphosphoremia as a complication. Conventionally, to prevent such complication, a phosphate binding agent of an aluminum compound, such as aluminum hydroxide or aluminum carbonate, has been administered to the patient. This type of phosphate binding agent, however, has little effect on the patient who takes a large amount of phosphorus (more than 1,500 mg/day) because of low phosphate adsorptivity of said binding agent. Further, administration of this type of binding agent in a large amount could develop adverse side effects such as constipation, nausea, vomitting, etc. Furthermore, it has been recently reported that aluminum accumulates in the patients with chronic renal failure to cause osteomalacia or encephalopathy.
On the other hand, a report has been made recently on the possible use of MgO alone as a phosphate adsorbent. Use of MgO alone, however, involves the serious problem that its storage and handling are very complicated and troublesome because MgO is susceptible to the presence of carbon dioxide in an atmosphere and when it is left there, its phosphate adsorptivity is reduced with time.
Further, there are several reports concerning phosphate adsorbents, such as U.S. Pat. No. 4,474,853 and Japanese Patent Application Laid-Open (KOKAI) Nos. 59-76,536 (1984) and 60-132,644 (1985). However, all these reports disclose zirconium compounds only as the adsorbent.
In view of these circumstances, the present inventors have studied extensively to provide an adsorbent which is highly safe in vivo, has excellent phosphate adsorbing characteristics and is capable of maintaining such characteristics for a long time and as a result have found that an MgO-TiO.sub.2 complex, comprising a specific composition, has 7 to 8 times higher phosphate adsorptivity than the conventional aluminum hydroxide type adsorbents, is capable of maintaining high phosphate adsorptivity for a long time and is quite apposite to the object of this invention. Furthermore, the present inventors have found that an adsorbent having said MgO-TiO.sub.2 complex deposited on an internal surface of active carbons shows a very excellent phosphate adsorptivity while maintaining inherent adsorbing characteristics of active carbons without being impaired.